In the field of oncology it is important to be able to discriminate tumor tissue from normal tissue. Golden standard is to inspect tissue at the pathology department after a biopsy or after surgical resection. A drawback of this current way of working is that real time feedback during the procedure of taking a biopsy or performing the surgical resection is missing. A way to provide instant feedback in case of, for instance, the biopsy needle is to incorporate fibers to perform optical measurements at the tip of the needle. Various optical methods can be employed with diffuse reflectance (DRS) and autofluorescence measurement as the techniques that are most commonly investigated. Several probes are used to perform these measurements but in general these probes have blunt end surfaces and are therefore not a direct integral part of the needle.
In U.S. Pat. No. 4,566,438 a sharp fiber-optic stylet is described in which two fibers are incorporated that could perform DRS and fluorescence measurements at the tip of the needle. However the fibers in the stylet are bevelled and as a result a significant part of the light in the fiber will undergo total internal reflecton at the tip of the needle, reaching the cladding material of the fiber and then exiting the fiber. This travelling through the buffer can cause a significant amount of unwanted autofluorecence of the cladding material hampering the measurement of the tissue autofluorescence.